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c Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
c Copyright (C) ????-2008 - INRIA - Serge STEER
c
c This file must be used under the terms of the CeCILL.
c This source file is licensed as described in the file COPYING, which
c you should have received as part of this distribution. The terms
c are also available at
c http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
C/MEMBR ADD NAME=WPRXC,SSI=0
c Copyright INRIA
subroutine wprxc(n,rootr,rooti,coeffr,coeffi)
c!but
c wprxc calcule les coefficients d'un polynome defini par ses
c racines (complexes) et dont le coefficient de degre maximum est 1
c
c!liste d'appel
c subroutine wprxc(n,rootr,rooti,coeffr,coeffi)
c double precision rootr(n),rooti(n),coeffr(n+1),coeffi(n+1)
c integer n
c
c n : degre du polynome
c root : tableau contenant les racines
c coeff : tableau contenant les coefficients du polynome, ranges
c par odre croissant
c!sous programmes appeles
c dset waxpy (blas)
c!
double precision rootr(n),rooti(n),coeffr(*),coeffi(*)
integer n
c
integer j,nj,ninf
double precision dlamch
c
ninf=0
c
call dset (n,0.0d+0,coeffr,1)
call dset (n+1,0.0d+0,coeffi,1)
coeffr(n+1)=1.0d+0
c
do 10 j=1,n
if(abs(rootr(j)).gt.dlamch('o').or.
$ abs(rooti(j)).gt.dlamch('o')) then
c . infinite roots gives zero high degree coeff
ninf=ninf+1
else
nj=n+1-j
c call waxpy(j,-rootr(j),-rooti(j),coeffr(nj+1),coeffi(nj+1),1
c $ ,coeffr(nj),coeffi(nj),1)
do k=nj,nj+j-1
coeffr(k)=coeffr(k)-rootr(j)*coeffr(1+k)+
$ rooti(j)*coeffi(1+k)
coeffi(k)=coeffi(k)-rootr(j)*coeffi(1+k)-
$ rooti(j)*coeffr(1+k)
enddo
endif
10 continue
if (ninf.gt.0) then
call unsfdcopy(n-ninf+1,coeffr(ninf+1),1,coeffr(1),1)
call dset(ninf,0.0d0,coeffr(n-ninf+2),1)
call unsfdcopy(n-ninf+1,coeffi(ninf+1),1,coeffi(1),1)
call dset(ninf,0.0d0,coeffi(n-ninf+2),1)
endif
c
return
end
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